National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS66 KEKA 232127
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
227 PM PDT Tue Apr 23 2024

.SYNOPSIS...Showers and thunderstorms have developed across portions
of interior this afternoon, mainly in Trinity county. A cooling
trend will start today, then drastically cooler interior
temperatures, rain and high mountain snow will develop Thursday
through Friday. Additional showers and below normal temperatures are
expected through the weekend.


&&

.DISCUSSION...An upper level low off the coast of Southern CA has
generated southerly winds over the Central Valley today, advecting
moisture over the Yolla Bollies and much of Trinity county.
Meanwhile, temperatures aloft have cooled as a weak shortwave moves
overhead. These features have destabilized the lower levels and
allowed convection to develop early this afternoon across Trinity
county, with thunderstorms currently occurring over the mountains,
and these are expected to continue for the next few hours at least.
Lapse rates aloft diminish through the afternoon to only around
6c/km and this may end convection by late afternoon.

Tuesday night is expected to be dry once the showers come to an end,
although drizzle may form again along the coast. Wednesday
widespread coastal stratus is expected to continue in the morning
and may take some time to clear back to near the coast. Inland a few
showers are possible again, but the threat for thunder looks lower
than this afternoon. The flow aloft will be out of the west which is
not a favorable pattern for convection, and soundings show a mid-
level cap developing across much of our area. Wednesday night is
expected to be mainly dry.

Thursday an upper level trough is expected to drop down from the
northwest bringing cooler air and some rain to the area. At this
point it looks like the rain will be starting in Humboldt and Del
Norte counties in the morning and is expected to spread south and
east in the afternoon. The front is expected to dissipate as it
moves south with southern Mendocino and Lake counties receiving very
little rain.

Friday and into the weekend the pattern remains cool and moist with
zonal onshore flow through the column. Shortwaves are expected to
move through this and bring some periods of light precipitation,
primarily to the Redwood Coast. Overall amounts are expected to be
light and snow levels will generally be above 4000 to 5000 feet.
Inland valley temperatures will likely see high temperatures
struggle to get out of the 50s on Friday with only some slight
warming going into the weekend. MKK


&&

.AVIATION...An offshore mesoscale low continues to migrate south
toward a broad area of low pressure off the Mendocino coast, driving
southwesterly return flow up the coastline. The marine inversion has
deepened to 3,000 feet, effectively capping the coastal terminals
beneath a thick layer of MVFR level stratus. Inland extent of
stratus dissipated some this afternoon with diurnal heating,
allowing UKI to see brief scattering of ceilings. Onshore WNW flow
will resume this evening, helping to re-enhance the marine layer
overnight. MVFR conditions will likely deteriorate to IFR early
Wednesday morning as westerly winds subside along the coast. Reduced
visibilities are possible at coastal terminals as low ceilings
struggle to lift out. UKI will remain clear beneath low stratus as
southerly winds diminish, becoming broken by Wednesday afternoon.


&&

.MARINE...Southerly winds gusts up to 35 mph were observed near Pt.
Arena and Crescent City this morning. These battling winds have
generated a complex short period wave environment with combined
significant heights of 5 to 7 feet. Winds have continued to weaken
and will turn into a more northerly and onshore flow this evening
and are forecasted to persist through Thursday. A series of mild
cold fronts will lightly enhance winds, though gusts are forecasted
to be moderate at best with 20 kt gusts restricted right around Cape
Mendocino. Such winds will most likely not even be strong enough to
even build short period seas to 6 feet. Though short period seas
will dominate the sea state through the week, a series of
persistent, mid period northwest swells up to 5 feet will generally
compliment the northerly wind waves. Friday morning shows signs of
more chaotic seas returning as strong north winds return, maxing out
south of Cape Mendocino. DS


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
None.
NORTHWEST CALIFORNIA COASTAL WATERS...
None.
&&

$$

Visit us at https://www.weather.gov/eureka

Follow us on Facebook and Twitter at:
https://www.facebook.com/NWSEureka
https://www.twitter.com/NWSEureka

For forecast zone information
see the forecast zone map online:
https://www.weather.gov/images/eka/zonemap.png